Pete/search api

Numerous fixes:

* caching geocoding requests - e.g. searching for 'Brighton, UK' or 'Newcastle' multiple times will only hit the geocoding API once for each search
* retrieving and re-displaying previous search API results from collection when going back to search results page, rather than creating a new API call each time
* adding initial search circle the first time you visit the search map page - circle radius is configurable from config file
* small tweaks to search sidebar - hiding components not currently implemented